Extraction of yttrium with molten monocarboxyl acids

A method has been developed for the determination the fluorine content from the induced activity of the short-lived nuclide²⁰F (T-11.4 s; E_λ=1.63 MeV) formed by the reaction¹⁹F(d,p)²⁰F. The method has been employed to determine fluorine in zirconium using a small-size 3 MeV deuteron accelerator for activation. The lower limit of fluorine detection is 0.5 ppm at the average deteron current of 0.3 μA.     

Application of particle induced gamma-ray emission for non-destructive determination of fluorine in barium borosilicate glass samples

Barium borosilicate glass (BaBSG) is proposed as a potential candidate for vitrification of nuclear waste generated from thoria based nuclear reactors. Along with fission products, activation products and many inactive chemicals, like fluorine in the form of HF are expected to be present in the dissolver solution with nuclear waste. As vitrification occurs at high temperature, it is important to quantify fluorine in BaBSG. Due to its complex matrix, most of the wet chemical and nuclear analytical methods encounter problems in the estimation of fluorine. Particle induced γ-ray emission (PIGE) method has been standardized for non-destructive determination of fluorine contents in BaBSG samples utilizing measurement of prompt gamma-rays from ¹⁹F (p, p’γ) ¹⁹F reaction. Experiments have been carried out with thick pellet targets prepared in cellulose matrix using 4 MeV proton beam from the folded tandem ion accelerator at BARC, Mumbai. For obtaining current normalized count rate of interest, beam current variation was monitored by the Rutherford backscattering spectrometry (RBS) method as well as by the in situ approach using an externally added element sensitive to PIGE. In this paper standardization of PIGE methods for F determination, validation of methods using synthetic samples, and application to BaBSG samples are reported.     

Epithermal/Fast Neutron Cyclic Activation Analysis for the Determination of Fluorine in Environmental and Industrial Materials

Pseudocyclic activation analysis (12-second irradiation, 12-second count, 5 cycles, 25 minutes between cycles) is used to determine fluorine in plastic and rubber with detection limits in the range 15–40 mg/kg. The detection of fluorine in materials containing high concentrations of aluminum is improved using the ¹⁹F(n,p)¹⁹O reaction, induced by fast neutrons, (30-second irradiation, 30-second count, 25-minute decay between cycles). The method was applied to a biomonitoring survey in the vicinity of an aluminum smelter in the Årdal region, Norway. The fluorine concentration in the moss and soil samples could be determined in all samples above the detection limits of 50 and 100 mg/kg, respectively.     

Kinetics of chlorine isotope exchange reaction between sodium chloride-36 and triphenyltin chloride in mixed solvents

Fluorine is an important trace element for life and human well-being. Food, in general, provides about 40 percent of the fluorine intake in the human body. In order to measure fluorine levels in human diet samples, Instrumental Neutron Activation Analysis (INAA) and Proton Induced Gamma-ray Emission (PIGE) analysis were used. Reactions¹⁹F(n,)²⁰F and¹⁹F(n, p)¹⁹O were employed for determination of the fluorine concentration using a reactor neutron spectrum and epithermal neutrons. Corrections were made for the sodium matrix interference caused by the²³Na(n, )²⁰F threshold reaction in the case of reactor neutron cyclic activation analysis and for the oxygen interference via¹⁸O(n, )¹⁹O reaction when using the epithermal cyclic NAA method. The fluorine content of the diet samples was also determined by PIGE analysis making use of the resonance reaction¹⁹F(p, )¹⁶O at 872 keV. Cyclic Neutron Activation Analysis (CNAA) when combined with mass fractionation was found to be the most suitable for determination of low concentration of fluorine, through the¹⁹F(n, )²⁰F reaction with a detection limit of 2.2 ppm in Bowen's Kale elemental standard.     

Determination of fluorine concentrations in soil samples using proton induced gamma-ray emission

A non-destructive, in situ current normalized particle induced gamma-ray emission methodology has been standardized for quantification of fluorine (F) in soil samples from Punjab state, India. The samples were irradiated using 4 MeV proton beam from the Folded Tandem Ion Accelerator at BARC, Mumbai. The gamma rays of energies 197 and 478 keV arising from ¹⁹F(p, p′γ)¹⁹F and ⁷Li(p, p′γ)⁷Li nuclear reactions were measured using high resolution gamma-ray spectrometry. The concentration of fluorine in soil samples was found to vary between 414 and 5,746 mg kg^?1.     

Chemical analysis with a low energy particle accelerator

The low energy particle accelerator at Brooklyn College is being applied to chemical analysis by studies of: charged particle induced nuclear reactions, proton induced X-ray emission, and inelastic neutron scattering. Fluorine-containing gaseous compounds in the atmosphere and fluorine in airborne particulates will be determined by detection of the prompt gamma-rays and/or alpha particles emitted in the reaction¹⁹F(p,a)¹⁶O. The PIXE technique is being applied to analysis of a variety of environmental samples, and activation by inelastic neutron scattering is being investigated for elements which are not amenable to thermal neutron activation. This work was supported in part by the U. S. Energy Research and Development Administration under Contract E(11-1)-3126.     

The 19F chemical shift in oxygen containing carbon fluorine products

We have examined the ¹⁹F NMR spectra of a number of oxygen-containing fluorocarbon products and obtained a comprehensive set of ¹⁹F chemical shift values, which enabled us to determine the influence of an oxygen atom bonded to a fluorocarbon group on the ¹⁹F chemical shift. The influence of neighbouring fluorocarbon groups, either directly connected or separated by an oxygen atom, was also considered. Our results may be summarized as follows. An oxygen atom bonded by a single bond (ether type bond) to a fluorine substituted carbon atom decreases the ¹⁹F chemical shift, as does the introduction of a further fluorine atom. Considering two adjacent fluorocarbon groups, a variation of x ppm in the ¹⁹F chemical shift of one of the two groups gives a variation of 0·12 x ppm in the opposite sense on the ¹⁹F chemical shift of the other group. If the two groups are connected by an ether oxygen atom, the effect is only about 0·06 x ppm.     

19F n.m.r spectra of polyfluoroquinolines. Long range inter-ring 19F?19F coupling constants and 19F chemical shifts

The signs and magnitudes of every fluorine–fluorine coupling constant in perfluoroquinoline ( 1 ), 2,4-dichloropentafluoroquinoline ( 2 ) and 2-bromohexafluoroquinoline ( 3 ) have been determined by ¹⁹F n.m.r. These provide an unambiguous assignment of the spectrum of the first compound and its derivatives. Inter-ring fluorine–fluorine coupling constants were found to be positive over an odd number of bonds and negative over an even number of bonds, similar to that observed in proton–proton coupling constants in multicyclic systems. The ¹⁹F chemical shifts of perfluoroquinoline and its protonated salt are reported and directly correlated with SCF MO calculated π-electron densities at both fluorine and bonded carbon atoms.     

Determination of fluorine in geological samples using accelerator derived neutrons

A fast, neutron activation analysis technique is described for the determination of fluorine in geological samples. The method utilises the reaction¹⁹F(n,α)¹⁶N for the determination. However, it avoids the interference reaction from oxygen which produces the same radionuclide since the neutrons are derived from the bombardment of beryllium with 3 MeV deuterons. The maximum energy of the neutrons so produced is well below the threshold for the competing oxygen reaction. The results indicate that the method gives acceptable accuracy over the range of a few tens ppm to several percent fluorine content using suitable standards. Sample analysis time is only a few minutes allowing the analyses of large numbers of samples per day.     

Proton microprobe determination of fluorine depth distributions and surface multielement characterization in dental enamel

Particle induced X-ray emission analysis (PIXE) and nuclear reaction analysis have been applied to multielemental analysis of human dental enamel in a proton microprobe. The PIXE technique was excercised for the characterization of multielemental lateral distributions on and just below the sample surface. For the assessment of depth distributions of fluorine the resonant nuclear reaction¹⁹F(p,aλ)¹⁶O was used. The combination of two analytical techniques comprising both atomic and nuclear interactions in a microprobe was applied to enamel samples of different origins. One sample constituted a healthy enamel and the other one enamel from a restored tooth. The microprobe in the combined mode was demonstrated to permit the establishment of lateral, concentration gradients of elements heavier than phosphorus with a resolution of 15 μm in enamel and simultaneously of depth distributions of fluorine better than 0.7 μm. The detection limits approached, 10–25 ppm for most of the elements considered. Supported by the Swedish Natural Science Research Council     

Der Einfluß von Fluor auf Die Photonenaktivierungsanalyse von Sauerstoff

By activation with high energy photons oxygen can be analysed down to about 40 ng using the nuclear reaction¹⁶O(γ,n)¹⁵O. In samples containing fluorine the analysis of oxygen is disturbed by the interferring reaction¹⁹F(γ,tn)¹⁵O. This reaction increases the analysis result of oxygen by 1.6% over the content of fluorine.     

Determination of fluorine in standard rocks by photon activation analysis

A highly sensitive determination of fluorine in standard rocks by photon activation using the¹⁹F(,n)¹⁸F reaction combined with pyrohydrolysis for the separation of¹⁸F has been reported. The irradiation energy was operated at 20 MeV to avoid the interference from Na, because Na is one of the major element in rocks and¹⁸F is also produced from Na via²³Na(,n)¹⁸F reaction above its threshold energy, 20.9 MeV. After irradiation, fluorine was extracted by pyrohydrolysis and separated as LaF₃ precipitate. It was ascertained that the average recovery of fluorine in standard rocks was about 90% and the precipitate was of high radiochemical purity. This method was applied to the analysis of ten GSJ rock reference samples and two USGS standard rocks issued by the Geological Survey of Japan and the United States Geological Survey, respectively. The detection limit of this method was 0.02 g/g, and the results obtained by this method were in good agreement with the recommended values. This method was easily applied to the determination of a few ppm level of fluorine in rock samples, such as ultrabasic rock and feldspar.     

A method for charged-particle activation analysis and its application to fluorine determination by the19F(p, αγ)16O reaction

A simple method for calculating the sensitivity for detecting a nuclide distributed uniformly in any given matrix through charged particle activation is described. This method takes into account the actual values of the reaction cross section at different energies as the beam traverses through a thick target and the corresponding stopping power values. The detection sensitivity for fluorine in a number of matrices through the¹⁹F(p, αγ)¹⁶O reaction have been calculated as a function of the energy from threshold to 4.16 MeV using this method and the sensitivity curves plotted. The sensitivity values (dps/ppm/μA) for a thick or thin target and even for a layer of known thickness at a particular depth within a sample can be directly read from these curves for known bombarding conditions. The comparator methods for charged particle activation analysis of RICCI¹ and of CHAUDHRI,² especially when the matrices of the sample and standard are different, have been compared in the case of F determination through the¹⁹F(p, αγ)¹⁶O reaction. It has been found that the errors are reduced by almost a factor of two when the latter method is used compared to the former one. The fluorine concentration in animal bones and teeth, apatite crystal, and rocks have been determined through the¹⁹F(p, αγ)¹⁶O reaction using the Melbourne University Pelletron.     

Rapid determination of fluorine in coral skeletons by non-destructive neutron activation analysis using 20F

A rapid non-destructive technique has been proposed for the determination of fluorine in coral skeletons by thermal neutron activation analysis, using the short half-life ²⁰F nuclide (11.0 s). About 0.2-0.5 g samples were irradiated for 10 seconds in a Triga Mark II Reactor. Soon after the irradiation (25-35 s), measurements of -rays were performed with each sample and standard. The method has the drawback of low sensitivity (20 ppm of F), and the manual operation employed in the cooling step could lead to less precise measurements. We determined fluorine in coral standards within ~8% of analytical precision. The result obtained for the dolomite standard was fairly consistent with literature values, but those for the limestone standard showed to be considerably higher than the reported values. The present method was applied for the determination of fluorine in modern corals from Khang Khao Island, Thailand and Okinawa, Japan. Two core samples of an ancient reef from Funafuti Atoll were measured for fluorine to compare with modern samples. In order to understand the environmental media in which coral grew, the partition of fluorine between seawater and coral skeletons is also discussed.     

Determination of fluorine in organic compounds by epithermal neutron activation analysis

Classical activation analysis of fluorine by thermal neutrons has a limited application because of frequent interference from chlorine, the short half life²⁰F (11.4 s) and too high dead time of detectors. A procedure is described for fluorine determination using¹⁹F (n,p)¹⁹O reaction. Use of a boron carbide shield has no effect on the activity of¹⁹O (boron ratio −1) but considerably reduces background and interference due to¹⁸O (n, γ)¹⁹O reaction. The technique has been successfully applied to the determination of fluorine in organic compounds even in the presence of large amounts of chlorine and oxygen.     

Determination of fluorine in geological materials by fast neutron activation based on the 19F(n,2n)18F reaction

The determination of fluorine in geological materials by fast neutron activation analysis based on the ¹⁹F(n, 2n)¹⁸F reaction is described. Fast neutrons are produced by irradiation of a thick beryllium target with 14.5 MeV deuerons. A rotating smple holder allows simultaneous irradiation of samples and standards. Fluorine-18 is separated by steam distillation of hexafluorosilicic acid or by extraction with triphenylatimony(V) dichloride and the annihilation radiation is measured with γ—γ coincidence equipment. The nuclear interference of recoil protons that induce the ¹⁸O(p,n)¹⁸F reaction is evaluated by means of synthetic samples: for a rock containing 43.4% of oxygen and 0.5% of hydrogen, the interference corresponds to 4.4 μg g^?1 fluorine. The method was applied to USGS and NIMROC reference rocks: for concentrations between 6000 and 50 μg g^?1, the relative standard deviation ranged from 2 to 10%.     

Optimation of fluorine detection for biological and geological applications with a nuclear microprobe

A review of the nuclear reactions used to determine fluorine is presented. In order to optimize the detection of fluorine in biological or in geological samples, a comparison of the performances obtained with the three nuclear reactions¹⁹F(p, ₀)¹⁶O,¹⁹F(p, )¹⁶O,¹⁹F(p, p')¹⁹F was made. The last reaction was chosen for its sensitivity. The homogeneity of biological and geological standard samples, the linearity of the calibration curves, and the stability of fluorine under the beam were tested.     

Activation analysis with cyclotron-produced fast neutrons. Application to instrumental multi-element analysis and to the radiochemical determination of fluorine

Fast neutrons produced by irradiation of a thick beryllium target with 20–50 MeV deuterons are used for activation analysis. The spatial neutron flux distribution around the target is measured. A rotating sample holder is used for the simultaneous irradiation of samples and standards. Instrumental analysis can be applied for a number of elements. As an example, results for calcium and strontium in some reference materials are given. The¹⁹F(n, 2n)¹⁸F reaction is used for the radiochemical determination of fluorine in rocks with a fluorine concentration ranging from 9 to 5400 μg·g⁻¹ Aspirant of the N.F.W.O.     

On the determination of sulfur by charged particle activation analysis

An analytical method is described for the determination of trace amounts of sulfur by charged particle activation analysis. The method consists of proton irradiation followed by a rapid radiochemical separation of the product nuclide,^34m Cl. This procedure has been applied to a number of pure metal samples which range in sulfur content from 0.3 to 30 ppm. All analyses were repeated several times to ensure consistent results and to better evaluate experimental detection limits and systematic errors. The results indicate that sulfur determinations can be performed at a concentration of less than 1.0 ppm. Activation curves are presented for the reactions S(d,x)^34mCl, S(p,x)^34mCl, and the interfering reaction³⁵Cl(p, pn)^34mCl. In memoriam.